Treatment of tuberculosis (TB) requires multi-drug regimen for a period of 6 to 9 months. One of the primary reasons for a long-term chemotherapy is the extraordinary ability of Mycobacterium tuberculosis, the causative agent of TB, to survive against drug exposure. Persistence of bacteria in their natural habitat is, in part, facilitated by their growth in multicellular structured community called biofilms. Persistence of chronic infections by several microbial pathogens such as Pseudomonas spp., Candida spp. or Streptococcus spp. has been attributed to their ability to form biofilms inside host. Therefore, in order to understand the persistence of M. tuberculosis against drug exposure we have been studying the development of its biofilms in an in vitro growth model. Our preliminary observation suggests that the biofilm formation by pathogen is controlled by both environmental and genetic factors. Upon evaluation of tolerance properties of M. tuberculosis biofilms against rifampicin and isoniazid we found that a significantly large number of bacilli in biofilms developed phenotypic resistance against both the antibiotics, whereas cells growing in planktonic suspension remained susceptible. This observation raises a fundamental question as to how these persisters develop within biofilms. One of the approaches in answering this question will be to understand the molecular basis of biofilm development by M. tuberculosis. I propose to investigate the environmental and genetic factors that control the biofilm development of M. tuberculosis. Identification of such factors will be very useful in understanding the development of persisters as wells as designing suitable strategies to targeting them. PUBLIC HEALTH RELEVANCE: Tuberculosis (TB), caused by Mycobacterium tuberculosis, kills nearly 2 million people in the world every year and takes 6 to 9 months of intensive chemotherapy for the treatment. Long-term persistence of M. tuberculosis against chemotherapy is a key hurdle in an effective treatment of TB. In this project we are addressing the persistence issue of M. tuberculosis by studying its growth and development in biofilms- the surface attached multicellular structures with significantly more drug tolerant persisters than planktonic cultures.